Apparatus and method for active vibration control of hybrid vehicle

ABSTRACT

The present disclosure relates to an apparatus and a method for active vibration control of a hybrid electric vehicle. Exemplary forms provide a method for active vibration control of a hybrid electric vehicle that may include detecting an engine speed or a motor speed; selecting a reference angle signal based on position information of a motor or an engine; establishing a period of fast Fourier transform (FFT) and performing FFT of the engine speed or the motor speed corresponding to the period of the FFT from the reference angle signal; establishing a reference spectrum according to an engine speed and an engine load; extracting a vibration components to be removed based on information of the reference spectrum; summing vibration components to be removed according to the frequencies and performing inverse FFT; determining an amplitude ratio according to the engine speed and the engine load; determining an adjustable rate such that a speed change amount of the engine is increased as an anti-phase torque is increased; and performing active vibration control of each frequency based on the information of the basic amplitude ratio, the adjustable rate, and the engine torque.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims priority to Korean Patent Application No.10-2015-0176940, filed in the Korean Intellectual Property Office onDec. 11, 2015, the entire contents of which are incorporated herein byreference.

BACKGROUND

(a) Field of the Disclosure

The present disclosure relates to an apparatus and a method for activevibration control of a hybrid electric vehicle. More particularly, thepresent disclosure relates to an apparatus and a method for activevibration control of a hybrid electric vehicle that controls unsteadyvibration by analyzing a frequency spectrum through fast Fouriertransform (FFT).

(b) Description of the Related Art

A hybrid vehicle is a vehicle using two or more different kinds of powersources, and is generally a vehicle that is driven by an engine thatobtains a driving torque by burning fuel and a motor that obtains adriving torque with battery power.

Hybrid electric vehicles can be provided with optimum output torque,depending on how the engine and the motor are operated while thevehicles are driven by the two power sources, that is, the engine andthe motor.

Hybrid electric vehicles may form various structures using the engineand the motor as power sources. Hybrid electric vehicles may beclassified as a TMED (Transmission Mounted Electric Device) type, inwhich the engine and the motor are connected by an engine clutch and themotor is connected to the transmission, or a FMED (Flywheel MountedElectric Device) type, in which the motor is directly connected to acrankshaft of the engine and connected to the transmission through aflywheel.

From among these, since the FMED type of the hybrid electric vehicle isvery noisy and has severe vibration, vibration reduction thereof isbeing studied. A method of frequency analysis which extracts thevibration component is normally used for this.

An analog method using a band pass filter has been used in aconventional frequency analysis, wherein the analog method of analysisdetermines whether or not a frequency is abnormal based on an amplitudeof each expected point of a frequency band.

However, distinguishing between the vibration component of the engineand the vibration of the noise component is difficult, and unnecessaryover-control of the vibration negatively affects aspects of controlefficiency and energy management. Further, because it is only possibleto create and synchronize a reference signal with respect to a specificfrequency in the conventional frequency analysis, comprehensive andactive control of other frequencies which may be additionally generatedis not performed.

The above information disclosed in this Background section is only forenhancement of understanding of the background of the disclosure andtherefore it may contain information that does not form the prior artthat is already known in this country to a person of ordinary skill inthe art.

SUMMARY

The present disclosure has been made in an effort to provide anapparatus and a method for active vibration control of a hybrid electricvehicle, having advantages of elaborately controlling an abnormalvibration component through an entire frequency spectrum analysis usingFFT (fast Fourier transform) and reflecting a change of a surroundingfrequency component in real time by feedback.

An exemplary form of the present disclosure provides a method for activevibration control of a hybrid electric vehicle that may includedetecting an engine speed or a motor speed; selecting a reference anglesignal based on position information of a motor or an engine;establishing a period of fast Fourier transform (FFT) and performing FFTof the engine speed or the motor speed corresponding to the period ofthe FFT from the reference angle signal; establishing a referencespectrum according to an engine speed and an engine load; extractingvibration components to be removed based on information of the referencespectrum; summing vibration components to be removed according to thefrequencies and performing inverse FFT; determining an amplitude ratioaccording to the engine speed and the engine load; determining anadjustable rate such that a speed change amount of the engine isincreased as an anti-phase torque is increased; and performing activevibration control of each frequency based on the information of thebasic amplitude ratio, the adjustable rate, and the engine torque.

The reference angle signal may be established by dividing by a number(m) of resolver poles based on information of the position of the motoror by selecting the reference angle between a top dead center (TDC) of anumber one cylinder and a bottom dead center (BDC) of a number fourcylinder based on information of the position of the engine.

The FFT period may be set in consideration of a cylinder and a stroke ofthe engine.

The analysis of the FFT signal may calculate a magnitude and phaseinformation of each frequency.

The frequency component that the FFT signal is greater than thereference spectrum may be selected as the vibration component to beremoved.

The vibration component to be removed may be removed by outputting themotor torque corresponding to an inverse value of a value by multiplyingthe reference signal created by inverse FFT, the engine torque, thebasic amplitude ratio and the adjustable rate.

Another exemplary form of the present disclosure provides a controlapparatus for active vibration control of a hybrid electric vehicleincluding an engine and a motor as a power source that may include aposition sensor configured to detect position information of the engineor the motor; a controller configured to select a reference angle signalon the basis of a signal from the position sensor, to perform fastFourier transform (FFT) of engine speed or motor speed, to extract avibration component to be removed through the FFT analysis, and toperform active vibration control of each frequency by performing inverseFFT; the controller may be configured to perform active vibrationcontrol of each frequency by reflecting a reference signal created bythe inverse FFT, a amplitude ratio, a predetermined adjustable rate suchthat the anti-phase torque is increased with the change of the enginespeed, and an engine torque.

The controller may be configured to establish a reference spectrumaccording to an engine speed and an engine load, and to extract thevibration component to be removed by comparing the reference spectrumwith the FFT signal.

The controller may be configured to sum the vibration components to beremoved according to frequencies, and to generate a reference signal byperforming inverse FFT.

The controller may be configured to determine an amplitude ratioaccording to an engine speed and an engine load, and to perform activevibration control of each frequency by reflecting the amplitude ratioand an engine torque.

The controller may be configured to remove the vibration component byoutputting the motor torque corresponding to an inverse value of a valueby multiplying the reference signal created by inverse FFT, the enginetorque and the basic amplitude ratio.

The controller may be configured to establish the reference angle bydividing by a number (m) of resolver poles based on information of theposition of the motor or to establish the reference angle between a topdead center (TDC) of a number one cylinder and a bottom dead center(BDC) of a number four cylinder based on information of the position ofthe engine.

The controller may be configured to establish an FFT period inconsideration of a cylinder and stroke of the engine, and analyzes theFFT signal by a calculated magnitude and phase information of eachfrequency.

As described above, in exemplary forms of the present disclosure, thevibration may be actively controlled, because the exact vibrationcomponent of each frequency may be extracted through FFT frequencyspectrum analysis. Therefore, since the determination system of thereference angle of the engine and the motor may be utilized as it is, anadditional device or an algorithm for signal synchronization as used inthe conventional art may be eliminated.

In addition, the adjustment amounts of vibration and a frequency whichis an object of the vibration control may be controlled individually, soit is possible to prevent inefficiency which is from the control whenthe vibration is over-removed and the fuel consumption may be improvedas the motor torque is increased when the engine is accelerated. Thus,precise and efficient active control may be performed through thefeedback control in real time.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic block diagram of an apparatus for active vibrationcontrol of a hybrid electric vehicle.

FIG. 2 is a flowchart illustrating a method for active vibration controlof a hybrid electric vehicle.

FIG. 3A to FIG. 3C are drawings illustrating vibration reduction towhich a method for active vibration control of a hybrid electric vehicleis applied in case that a change amount of an engine speed is increased.

FIG. 4A to 4F are graphs for explaining a method for active vibrationcontrol of a hybrid electric vehicle.

DETAILED DESCRIPTION

In the following detailed description, only certain exemplary forms ofthe present disclosure have been shown and described, simply by way ofillustration. As those skilled in the art would realize, the describedforms may be modified in various different ways, all without departingfrom the spirit or scope of the present invention.

Throughout this specification and the claims which follow, unlessexplicitly described to the contrary, the word “comprise” and variationssuch as “comprises” or “comprising” will be understood to imply theinclusion of stated elements but not the exclusion of any otherelements.

Like reference numerals designate like elements throughout thespecification.

It is understood that the term “vehicle” or “vehicular” or other similarterm as used herein is inclusive of motor vehicles in general includinghybrid vehicles, plug-in hybrid electric vehicles, and other alternativefuel vehicles (e.g., fuels derived from resources other than petroleum).As referred to herein, a hybrid electric vehicle is a vehicle that hastwo or more sources of power, for example both gasoline-powered andelectric-powered vehicles.

Additionally, it is understood that some of the methods may be executedby at least one controller. The term “controller” refers to a hardwaredevice that includes a memory and a processor configured to execute oneor more steps that should be interpreted as its algorithmic structure.The memory is configured to store algorithmic steps and the processor isspecifically configured to execute said algorithmic steps to perform oneor more processes which are described further below.

Furthermore, the control logic of the present disclosure may be embodiedas non-transitory computer readable media on a computer readable mediumcontaining executable program instructions executed by a processor, acontroller, or the like. Examples of computer readable media include,but are not limited to, ROM, RAM, compact disc (CD)-ROMs, magnetictapes, floppy disks, flash drives, smart cards, and optical data storagedevices. The computer readable recording medium can also be distributedin network coupled computer systems so that the computer readable mediaare stored and executed in a distributed fashion, e.g., by a telematicsserver or a controller area network (CAN).

An exemplary form of the present disclosure will hereinafter bedescribed in detail with reference to the accompanying drawings.

FIG. 1 is a schematic block diagram of an apparatus for active vibrationcontrol of a hybrid electric vehicle.

As shown in FIG. 1, an apparatus for active vibration control of ahybrid electric vehicle includes an engine 10, a motor 20, a positionsensor 25, a clutch 30, a transmission 40, a battery 50, and acontroller 60.

The engine 10 outputs power by combusting fuel as a power source whileturned on. The engine 10 may be various disclosed engines such as agasoline engine or a diesel engine using conventional fossil fuel. Therotation power generated from the engine 10 is transmitted to thetransmission 40 side through the clutch 30.

The motor 20 is operated by a 3-phase AC voltage applied from thebattery 50 through an inverter to generate torque, and operates as apower generator and supplies regenerative energy to the battery 50 in acoast-down mode.

In the exemplary form of the present disclosure, the motor 20 may bedirectly connected to the crankshaft of the engine 10.

The position sensor 25 detects position information of the engine 10 orthe motor 20. The position information of the engine 10 or the motor 20are transmitted to the controller 60.

That is, the position sensor 25 may include a crankshaft position sensorthat detects a phase of the crankshaft or a motor position sensor thatdetects a position of a stator and a rotor of the motor.

The controller 60 may calculate an engine speed by differentiating therotation angle detected by the crankshaft position sensor, and a motorspeed may be calculated by differentiating the position of the statorand the rotor of the motor detected by the motor position sensor.

The position sensor 25 may be additional speed sensor (not shown) formeasuring the engine speed or the motor speed.

The clutch 30 is disposed between the motor 20 connected to thecrankshaft of the engine 10 and the transmission 40, and switches powerdelivery to the transmission 40. The clutch 30 may be applied as ahydraulic pressure type of clutch or dry-type clutch.

The transmission 40 adjusts a shift ratio according to a vehicle speedand a running condition, distributes an output torque by the shiftratio, and transfers the output torque to the driving wheel, therebyenabling the vehicle to run. The transmission 40 may be applied as anautomatic transmission (AMT) or a dual clutch transmission (DOT).

The battery 50 is formed with a plurality of unit cells, and a highvoltage for providing a driving voltage to the motor 20 is stored at thebattery 50. The battery 50 supplies the driving voltage to the motor 20depending on the driving mode, and is charged by the voltage generatedfrom the motor 20 in the regenerative braking.

The controller 60 selects a reference angle signal on the basis of asignal from the position sensor, performs fast Fourier transform (FFT),extracts a vibration component to be removed the FFT analysis, andperforms active vibration control of each frequency by performinginverse FFT.

That is, the controller 60 sets up a reference spectrum according to aspeed and load of the engine, extracts a vibration component of eachfrequency by comparing the reference spectrum with the FFT signalanalysis result, and generates a reference signal by performing inverseFFT after selecting and summing a removal object frequency from eachfrequency vibration through FFT analysis. The reference signal may meanan inverse FFT signal of the vibration components to be removedaccording to frequencies.

In addition, the active vibration control of each frequency is performedconsidering a basic amplitude ratio according to an engine speed andload, and a adjustable rate which is predetermined such that theanti-phase torque is increased with the change of the engine speed andengine torque

For these purposes, the controller 60 may be implemented as at least oneprocessor that is operated by a predetermined program, and thepredetermined program may be programmed in order to perform each step ofa method for active vibration control of a hybrid electric vehicleaccording to an exemplary form of the present disclosure.

Various forms described herein may be implemented within a recordingmedium that may be read by a computer or a similar device by usingsoftware, hardware, or a combination thereof, for example.

In hardware implementations, the forms described herein may beimplemented by using at least one of application specific integratedcircuits (ASICs), digital signal processors (DSPs), digital signalprocessing devices (DSPDs), programmable logic devices (PLDs), fieldprogrammable gate arrays (FPGAs), processors, controllers,micro-controllers, microprocessors, and electric units designed toperform any other functions.

In software implementations, forms such as procedures and functionsdescribed in the present forms may be implemented by separate softwaremodules. Each of the software modules may perform one or more functionsand operations described in the present disclosure. A software code maybe implemented by a software application written in an appropriateprogram language.

Hereinafter, a method for active vibration control of the hybridelectric vehicle according to an exemplary form of the presentdisclosure will be described in detail with reference to FIG. 2 to FIG.4.

FIG. 2 is a flowchart illustrating a method for active vibration controlof a hybrid electric vehicle according to an exemplary form of thepresent disclosure, and FIG. 3A to FIG. 3C are drawings illustratingvibration reduction to which a method for active vibration control of ahybrid electric vehicle is applied in case that a change amount of anengine speed is increased.

As shown in FIG. 2, an active vibration control method of the hybridelectric vehicle is started when the position sensor 25 detects positioninformation of the engine 10 or the motor 20 at step S100, and thecontroller 60 may detect engine speed or motor speed using the positioninformation of the engine 10 or the motor 20 at step S100 (refer to FIG.4A).

The controller 60 selects the reference angle signal based on the signalof the position sensor 25 at step S110. That is, the controller 60selects the reference angle signal according to information of positionsof the engine 10 and the motor 30 (refer to FIG. 4A).

The controller 60 may set up the reference angle signal by dividing by anumber (m) of resolver poles based on information of the position of themotor 20, or may set up the reference angle signal between top deadcenter (TDC) of the number one cylinder and bottom dead center (BDC) ofthe number four cylinder based on information of the position of theengine 10.

For example, the controller 60 may select the reference angle signalbased on the information of the position of the motor 20, and may createthe reference angle signal by dividing 16 poles signal into eight (8).The reference angle signal means a start point for performing FFT.

After that, the controller 60 sets up a period of the FFT for performingthe FFT at step S120.

The controller 60 may set up the entire period in consideration of acylinder and stroke of the engine 10. For example, if the engine 10 hasfour cylinders and four strokes, the crank angle may be 720 degrees.

When the FFT period is set up in the step S120, the controller 60performs the FFT at step S130. That is, the controller 60 performs theFFT of the engine speed or the motor speed corresponding to the periodof the FFT from the reference angle signal (refer to FIG. 4B).

The controller 60 may calculate magnitude and phase information of eachfrequency by analyzing the FFT signal.

In addition, the controller 60 sets up a reference spectrum according tothe engine speed and load at step S140 (refer to FIG. 4B). That is, thecontroller 60 may set up a vibration reference value of each frequencyaccording to an operating point.

When the reference spectrum is set up in the step S140, the controller60 extracts a vibration component to be removed by comparing the FFTsignal with the reference spectrum at step S150.

That is, the controller 60 may select an object requiring vibrationcontrol in a compared result value of the FFT analysis and thepredetermined vibration reference value. The controller 60 may extractthe frequency component that the FFT signal is greater than thereference spectrum as the vibration component to be removed. Forexample, referring to FIG. 4B, f2 frequency component may be selected asa frequency component to be removed.

Since the reference spectrum means normal vibration components accordingto the engine speed and load, the controller 60 determines the frequencycomponent that the FFT signal is greater than the reference spectrum asabnormal vibration components to be removed.

When the vibration components to be removed is selected in the stepS150, the controller 60 sums the vibration components to be removedaccording to frequencies, and performs inverse FFT to create a referencesignal at step S160 (refer to FIG. 4C). As described above, thereference signal means inverse FFT (IFFT) signal of the vibrationcomponents to be removed.

In addition, the controller 60 determines an amplitude ratio accordingto an engine speed and an engine load, and reflects an engine torque atstep S170.

That is, the controller 60 may input the amplitude ratio and the enginetorque according to an operating point of the engine into the referencesignal generated by the inverse FFT.

Herein, the amplitude ratio according to the engine speed and the engineload may be determined in advance by a predetermined map.

That is, the controller 60 may remove all the positive components andnegative components of the vibration components by outputting the motortorque corresponding to an inverse value of a value by multiplying thereference signal created by inverse FFT, the engine torque and the basicamplitude ratio (refer to FIG. 4D).

Since the reference signal is expressed as speed according to time, thecontroller 60 removes the vibration components to be removed byreflecting the engine torque and the basic amplitude ratio to thereference signal and transforming the reference signal to torquecomponent.

That is, as shown in FIGS. 4E and 4F, it is possible to control theengine speed or the motor speed that the frequency componentscorresponding to the reference spectrum are remained.

Referring to FIG. 3A, a magnitude and phase of vibration components ofeach frequency calculated by performing FFT analysis is illustrated.

Referring to FIG. 3B, anti-phase torque values which overlap thecomponent of vibration to be removed as indicated is illustrated. Thatis, the vibration components of each frequency and the anti-phase torqueas described in the FIGS. 3A and 3B can be reflected, thereby it can becontrolled such that the object to be removed may be removed and arequired vibration component remains as described in the FIG. 3C.

At this time, if the engine 10 is accelerating in which the changeamount of the engine speed is increasing, the predetermined adjustablerate may be determined so as to increase the anti-phase torque at stepS180. Referring to 3B, anti-phase torque values which overlap thecomponent of vibration to be removed as indicated is illustrated by adotted line. Here, if the change of the engine speed is increased, theadjustable rate may be set up such that the anti-phase torque is offsetand increased in a positive direction as indicated by a solid line.

After that, the controller 60 performs active vibration control based oninformation of the amplitude ratio, the adjustable rate, and the enginetorque of each frequency at step S180. That is, the controller 60 mayremove all the positive components and negative components of thevibration components by outputting the motor torque corresponding to aninverse value of a value by multiplying the reference signal created byinverse FFT, the engine torque, the basic amplitude ratio and thepredetermined adjustable rate.

Referring to FIGS. 3A and 3B, the adjustable rate is applied to thevibration component extracted through the FFT analysis, and since theincreased inverse torque when the change amount of the engine speed isincreased is reflected, it is controlled such that the object to beremoved is removed and a required vibration component remains, and thetorque indicated by the dotted line in increased as indicated by thesolid line as described in FIG. 3C.

FIG. 3C is a drawing illustrating vibration reduction to which apredetermined adjustable rate that increases a reverse phase torque as achange amount of an engine speed is increased is applied.

As described above, according to exemplary forms of the presentdisclosure, the vibration may be actively controlled, because the exactvibration component of each frequency may be extracted through FFTfrequency spectrum analysis. Therefore, since the determination systemof the reference angle of the engine and the motor may be utilized as itis, an additional device or an algorithm for signal synchronization asused in the conventional art may be eliminated.

In addition, because the adjustment amount of vibration and frequencywhich is the object of the vibration control may be controlledindividually, it is possible to prevent inefficiency which is from thecontrol when the vibration is over-removed and the fuel consumption maybe improved as the motor torque is increased when the engine isaccelerated. Thus, precise and efficient active control may be performedthrough the feedback control in real time.

While this invention has been described in connection with what ispresently considered to be practical exemplary forms, it is to beunderstood that the disclosure is not limited to the disclosed forms. Onthe contrary, it is intended to cover various modifications andequivalent arrangements included within the spirit and scope of theappended claims.

What is claimed is:
 1. A method for active vibration control of a hybrid electric vehicle, comprising: detecting an engine speed or a motor speed; selecting a reference angle signal based on position information of a motor or an engine; setting up a period of fast Fourier transform (FFT) and performing FFT of the engine speed or the motor speed corresponding to the period of the FFT from the reference angle signal; establishing a reference spectrum according to an engine speed and an engine load; extracting vibration components to be removed based on information of the reference spectrum; summing vibration components to be removed according to the frequencies and performing inverse FFT; determining an amplitude ratio according to the engine speed and the engine load; determining an adjustable rate such that a speed change amount of the engine is increased as an anti-phase torque is increased; and performing active vibration control of each frequency based on the information of the basic amplitude ratio, the adjustable rate, and the engine torque.
 2. The method of claim 1, wherein the reference angle signal is established by dividing by a number (m) of resolver poles based on information of the position of the motor or the reference angle is set up between a top dead center (TDC) and a bottom dead center (BDC) of a number one cylinder or a number four cylinder based on information of the position of the engine.
 3. The method of claim 1, wherein the FFT period is set in consideration of a cylinder and a stroke of the engine.
 4. The method of claim 1, wherein the analysis of the FFT signal calculates a magnitude and phase information of each frequency.
 5. The method of claim 1, wherein the frequency component in which the FFT signal is greater than the reference spectrum is selected as the vibration component to be removed.
 6. The method of claim 1, wherein the vibration component to be removed is removed by outputting the motor torque corresponding to an inverse value of a value by multiplying the reference signal created by inverse FFT, the engine torque, the basic amplitude ratio and the adjustable rate.
 7. An apparatus for active vibration control of a hybrid electric vehicle including an engine and a motor as a power source, comprising: a position sensor configured to detect position information of the engine or the motor; and a controller configured to select a reference angle signal on the basis of a signal from the position sensor, to perform fast Fourier transform (FFT) of engine speed or motor speed, to extract a vibration component to be removed through the FFT analysis, and to perform active vibration control of each frequency by performing inverse FFT; wherein the controller is configured to perform active vibration control of each frequency by reflecting a reference signal created by the inverse FFT, an amplitude ratio, a predetermined adjustable rate such that the anti-phase torque is increased with the change of the engine speed, and an engine torque.
 8. The apparatus of claim 7, wherein the controller is configured to establish a reference spectrum according to an engine speed and an engine load, and to extract the vibration component to be removed by comparing the reference spectrum with the FFT signal.
 9. The apparatus of claim 8, wherein the controller is configured to sum the vibration components to be removed according to frequencies, and to generate a reference signal by performing inverse FFT.
 10. The apparatus of claim 9, wherein the controller is configured to determine an amplitude ratio according to an engine speed and an engine load, and to perform active vibration control of each frequency by reflecting the amplitude ratio and an engine torque.
 11. The apparatus of claim 10, wherein the controller is configured to remove the vibration component by outputting the motor torque corresponding to an inverse value of a value by multiplying the reference signal created by inverse FFT, the engine torque and the basic amplitude ratio.
 12. The apparatus of claim 7, wherein the controller is configured to establish the reference angle signal by dividing by a number (m) of resolver poles based on information of the position of the motor or to establish the reference angle signal between a top dead center (TDC) and a bottom dead center (BDC) of of a number one cylinder or a number four cylinder based on information of the position of the engine.
 13. The apparatus of claim 7, wherein the controller is configured to establish an FFT period in consideration of a cylinder and stroke of the engine, and to analyze the FFT signal by a calculated magnitude and phase information of each frequency. 